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 “A” above. Each of these values is then multiplied by the corresponding luminosity valence, and the products thus obtained are reduced, with ratios unchanged, so that their sum is equal to unity. These figures are now multiplied separately by the percentage measure specified for the “white.” Either one of these operations—for average noon sunlight or the arbitrary “white”— yields a set of three figures, one for each of the excitations. (b) The next step is to treat the “per cent. hue” measure in a similar manner. The excitation values for the wave-length employed in the given match must first be looked up in. Each of the values thus found is next multiplied by the corresponding luminosity valence and the products are reduced so that their sum is equal to unity. Each of the resulting values must now be multiplied by the percentage measure of the monochromatic component in the original specification. (c) The corresponding members of the two sets of values, thus secured,—for the “white” and “hue” respectively—are now added. (d) The three resulting sums express the excitation values of the monochromatic specification in luminosity terms. In order to reconvert them into the color valence terms of, each of these sums must be divided by the corresponding luminosity valence, and the values thus obtained reduced to the usual percentage form.

In the case of specifications by monochromatic analysis, of colors possessing a purple hue, in terms of per cent. of the given color and the per cent. of its spectral complementary required to be mixed with it to match the standard white, the procedure for reduction of the data to excitation values differs from the above in the following way. (a) The “white” is treated exactly as described under “(a)” of the preceding paragraph, except that the final percentage employed as a multiplier is 100. (b) The complementary monochromatic stimulus is treated exactly as under “(b)” in the same paragraph, the final percentage multiplier representing the per cent. which this stimulus is of the mixture comprising it and the measured color. (c) The individual members of the set of values thus obtained for the complementary stimulus are then subtracted from the corresponding members of the set obtained for the white. (d) The three resulting differ